The present invention relates generally to sleeping bags and particularly to sleeping bags useful over a wide temperature range.
Sleeping bags are generally constructed for use in two different ways. Certain bags allow an individual to sleep with his head outside the bag, fully exposed to the environment. Thus, in warm or cool weather conditions, the individual may directly breathe fresh air. Other sleeping bags are constructed such that the individual may sleep completely inside the bag. In these latter constructions, the sleeping bag is formed of materials having a high level of air porosity enabling the air to easily defuse through the bag. In using either of these types of bags, however, an individual may suffer significant body heat loss, discomfort and cold injury. Also, those bags lack any type of humidity control.
Additionally, the operational temperature range of both types of bags is limited. For example, the open-type bag may not be useful in extreme cold weather conditions. Conversely, the closed bag may not be useful under warm conditions. Heat loss, humidity control and comfort can also be significant problems when using those bags. For example, when an individual sleeps with his or her head outside the bag and breathes bitter cold air, it can be quite uncomfortable, as well as a source of tremendous heat loss, possibly resultig in cold injury. On the other hand, while sleeping wholly within the bag promotes comfort and curtails heat loss, humidity levels may occur which could create undesirable condensation in certain areas within the sleeping bag. Humidity control is extremely important. Dehydration of the body and potential hypothermia because of respiration loss of moisture through the lungs can be very serious problems in extreme cold weather. Such moisture loss must be compensated for from another source and that, in turn, may create an additional problem in certain environments.